Raster graphics are the pictorial imaging graphics produced by most commercial cameras, scanners and drawing tablets. The images are comprised of arrays of small screen areas (lighted pixels) or printed dots. Each pixel or dot is associated with a value for tint and shade. High-resolution raster files can be produced high-quality imagery and are easily transmitted through line by line transmission.
The raster graphics system is great for reproducing surfaces of color and texture, which makes the system work very well for photography. However, the system is not good for reproducing lines. The raster line is a series of pixels, really a narrow version of a surface. Raster graphics are not easily scalable. When a raster image is enlarged, the pixels comprising the image are either made larger or separated so that edges become jagged or pixilated.
Most technical design tasks require line drawings. Computer-aided drafting (CAD) programs imitate the process of hand drafting by allowing operators to draw detailed plans using straight lines and curves. These technical tasks make use of vector images rather than raster images. Vector images are produced as a series of graphs of mathematical functions (slopes and lengths) between points called nodes. These line drawings are completely scalable by changing the values plugged into the formulas at each point. Drafting software enables the operator to make these changes using a mouse to pull the nodes into new positions or by simply entering new global values into a table. Most modern CAD programs allow the operator to color surfaces within the lines by applying bitmap surfaces as well.
To print vector graphics the images are usually converted back into raster format and printed on conventional printers. Vector images can also be printed using a pen plotter which is programmed to read the formulas represented in the vector drawing program and move the printing paper appropriately to reproduce the drawing using a series of pens.
It is common to convert graphics from raster to vector form to take advantage of the scalability and to make sketches readable in CAD software for modification and development. The process of converting from a raster image involves increasing the contrast of the raster image then using the capacity of most raster graphics software to find edges between color surfaces. The software can convert the edges into mathematical formulas and produce vector graphics along them. The operator can then adjust the resulting vector graphic by pulling the nodes into position to more accurately cover the raster edges and correct errors.
Large-scale conversion from raster to vector graphics can be a very labor intensive and tedious process. CAD / CAM Services has the expertise to do this on an industrial scale. For more information contact us.